The present invention concerns a new method for producing disposable microcuvettes or microdevices.
A microcuvette for sampling a fluid, mixing the sample with a reagent and directly making optical analyses of the sample mixed with the reagent is previously known from U.S. Pat. No. 4,088,448. This cuvette comprises a body member including two planar surfaces defining an optical path and placed at a predetermined distance from one another to determine the optical path length and to define a cavity having an inlet communicating said cavity with the exterior of the body member.
The cavity has a predetermined fixed volume, and the predetermined distance is chosen so as to permit the sample to enter the cavity by capillary force. Furthermore, a reagent is applied on the cavity surface.
This known cuvette has several advantages when compared with the conventionally used devices. It permits sampling of a liquid, mixing and chemically reacting it with a suitable reagent for e.g. colour development in the same vessel as the one used for the subsequent measurement. The cuvette disclosed in U.S. Pat. No. 4,088,448 thus simplifies the sampling procedure, reduces the number of utensils and, depending on the type of analysis, considerably improves the exactitude of the analysis by making the analysing procedure independent of the operating technique of the operator making the analysis.
At present microcuvettes based on the microcuvette disclosed in U.S. Pat. Nos. 4,088,488 and 5,674,457 are marketed for analysing e.g. hemoglobin and glucose. The accuracy and precision in the currently used cuvette production is excellent. An obvious disadvantage is that each cuvette has to be moulded in one piece and a specific tool is required for every type of cavity. Another disadvantage is the comparatively short stability due to the decomposition of the reagent mixture in e.g. the glucose cuvettes. The instability originates from the fact that different components of the reagents cannot be physically separated during the storage as, during the manufacture, the reagents are incorporated into the cuvette as a solution, which is subsequently dried. The dried reagent layer formed in the cuvette cavity therefore includes an intimate mixture of different reagent components. Furthermore, the design, particularly the depths of cuvettes having more than one cavity, cannot be selected at will and in view of the specific requirements for the specific analytical determination, but is restricted by the manufacturing method. For instance it is not possible to produce a cuvette having two cavities with different depths, of which the deepest cavity is most remote from the inlet opening by the current cuvette manufacturing technique.
In view of these problems with the presently used cuvettes and the manufacturing thereof a new manufacturing method, which satisfies the following conditions, is desired. The new manufacturing method should fulfil the following requirements:
It should make it possible to separate reagents, which would give the cuvette a prolonged stability.
It should be possible to effectively control the reagent distribution and separation of reagent components on the surface of the cavity.
It should permit a high flexibility in the choice of the cavity design.
It should permit the production of microcuvettes for photometric analysis with both high accuracy and precision.
It should permit the production of microcuvettes, wherein a deeper cavity is provided more remote from the sample inlet opening than a more shallow, capillary inlet cavity. The deeper cavity could be capillary or non-capilllary. When capillary, the deeper cavity is less capillary than the capillary inlet cavity.
It should permit continuous, high capacity production.
It should permit a modular production system, where the modules could be replaced or easily modified for a particular application.
It has now been found that these conditions can be satisfied by using the new manufacturing method according to the present invention.